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Topic: IR SPECTROSCOPY HELP NEEDED URGENTLY!  (Read 2556 times)

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Offline bull3396945

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IR SPECTROSCOPY HELP NEEDED URGENTLY!
« on: January 28, 2010, 02:49:58 AM »
Hi,
Could anybody please help me understand and solve these questions before 29th Jan?
I would really appreciate it if any kind of information regarding the questions is shared. Below are the questions...Thankyou so much.

1, Infrared spectroscopy is a good way to distinguish between certain possible isomeric structures. How (what peaks might be present or absent) would the following pairs of isomeric compounds be distinguished? Clearly indicate where the peaks should be or what peaks would be missing, with an approximate wavenumber region. (3 marks each even though there might be less than 3 or more than 3 reasons)
Please see attachment Question1.


2. A student attempts to synthesize the acetylenic compound using the following sequence.
Please see atachment Question 2.

The final isolated product has the following ms and ir spectral data:
mass spectrum of final product: m/z(%) 110(55), 95(100), 67(100), 55(38), 53(24), 41(76), 39(73), 27(38)
ir (selected peaks) cm-1, (intensity) 3022(m), 2850-3000(several, strong), 2723(w), 1623(m), 843(s)
(a) The final product could be called “diisopropylacetylene”. What would be the proper IUPAC name? (1 mark)
(b) What is the stereochemistry of the dibromo compound if the reaction is done in the “cold and dark”? (2 marks)
(c) What is the ‘normal’ frequency for the acetylene CC stretch? (You will have to look this up.) Should the final product show this peak? Why not? (3 marks)
(d) Considering the infrared data, what is the most likely structure for the final compound, given that the formula really is C8H14? (5 marks)
(e) We haven’t yet done C-13 NMR but each unique carbon shows up as a single line. The C-13 NMR of the final product shows 4 lines. How is this inconsistent with the proposed acetylene and how would this agree with the structure proposed in (d)?
(f) A text which we once used in this course lists ΔHfo for-1,3-butadiene and +26.2 kcal mole-1 and that for 2-butyne as +34.7 kcal mole-1. How is this consistent with the actual result of the attempted synthesis? (3 marks)

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